feat: add option to exclude specific default metrics from collection

[kwaszczuk]

Fixes: #623 (I believe it was incorrectly marked as fixed)

This PR adds exclude option to the DefaultMetricsCollectorConfiguration that allows to omit certain group of metrics from being collected.

My own use case is that I use a custom implementation of eventLoopLag metrics (though based on the original one), so I need to exclude them to avoid conflicts in registry, but others may want to also use it to remove redundant and unused metrics.

An alternative approach would be to expose the exports from lib/metrics in the public interface, allowing users to import and manually register only the specific metrics they need. I’m not sure, though, which approach is better - this one or the exclude approach.

[jdmarshall]

LGTM.

@zbjornson @SimenB how do we feel about this one?

[jdmarshall]

Needs a changelog entry.

[zbjornson]

LGTM too. Either approach (include or exclude) seems reasonable.

Needs a changelog entry.

Tangent, but I've wondered if we should remove this requirement and instead make it part of the maintainers' release process. It always creates merge conflicts when any other PR is merged.

[cjihrig]

Tangent, but I've wondered if we should remove this requirement and instead make it part of the maintainers' release process. It always creates merge conflicts when any other PR is merged.

FWIW, the OpenTelemetry project also requires contributors to add changelog entries with PRs and it is a massive pain when trying to contribute. Big +1 to removing that requirement.